1. Field of the Invention
The present invention relates generally to the field of Emitter Coupled Logic (ECL) circuits, and specifically to an ECL circuit accepting single-ended and differential inputs.
2. Description of Related Art
As is well known in the art, a basic ECL circuit consists of a differential amplifier. The differential amplifier consists of two parallel current paths, each controlled by an input level. Each input level provides a base voltage for a transistor controlling the current path. The digital state of the differential amplifier is determined by which of the two paths pass the most current.
There are two ways in which a ECL circuit is typically configured. The most common configuration is where one input to the differential amplifier is held constant at a fixed intermediate voltage, thereby allowing the other input to control the state of the differential amplifier (i.e., single-ended operation). In an alternative configuration, each of the complimentary outputs from a previous gate may be connected as complimentary inputs to the differential amplifier (i.e., differential operation).